Non-impact recording methods in the form of ink jet printing, thermal transfer printing and thermal sublimation printing are presently of considerable interest because of their capability for achieving high print speeds, their quiet operation and their capability for producing full color, highlight color and monochrome recordings. The present invention will be described relative to the ink jet recording process, although it should be understood that it is equally applicable to other recording techniques employing scanning recording heads.
In such scanning type printers, the recording heads are mounted upon a reciprocable carriage which is selectively moved across the recording substrate to record a single line of information. Then the recording substrate is moved normal to the scanning direction by a single line increment and recording is repeated while scanning with the recording heads, in either the same or the opposite direction. Each recording head includes an array of mark producing elements arranged in a direction generally parallel to the direction of movement of the recording substrate. The full page is printed one full line at a time. A scanning-type printer of this type, of the monochrome variety having a single head cartridge, is disclosed in U.S. Pat. No. 4,628,332 (Matsumoto) wherein the recording head cartridge is mountable onto a cartridge holder which, in turn, is mounted on the scanning carriage.
The ink jet recording process, in the form to which the present invention applies, involves the selective propulsion of droplets of an ink recording liquid from a scanning recording head onto a spaced recording substrate (such as paper or a projection transparency) upon which it adheres and dries. Propulsion may be accomplished by any one of several known methods for imparting pressure increases to confined portions of the ink adjacent the ejection orifice. Examples of such pressure inducing devices are piezoelectric elements, acoustic generators, magnetic compressors or heater elements. The latter device, for creating a drop-on-demand, initially heats the confined ink to rapidly expand it into a bubble which then bursts, forming a pressure wave which expells a droplet quantity of ink through the nozzle orifice. This method has gained in popularity because it is possible to simply and inexpensively fabricate the nozzle orifices and driving heaters by photolithographic thin film electronic methods, so as to produce recording heads including a dense array of orifices and related drivers (e.g. 50 per 1/6 inch) for recording images of high resolution. Another advantage of the heater-type pressure transducers is their capability of very fast refiring times, enabling high speed operation.
The cartridge method of ink jet printing lends itself to full-color printing and highlight color printing as readily as it does to monochrome printing. In monochrome printing a single cartridge (usually black) is moved by the reciprocable carriage. In full-color printing, several recording head cartridges containing colored inks (yellow, cyan and magenta) are mounted for scanning movement upon the carriage along with a black ink containing cartridge. It is possible, however, to produce process black by adding the three colors. Highlight color requires only two cartridges, usually black and one other color, such as red or yellow. In U.S. Pat. No. 4,528,576 (Koumura et al) there is disclosed a full-color ink jet printer of the type including four heads. These are shown arranged in two configurations: one is the well known side-by-side orientation, and the other is a stacked orientation in which the four heads are positioned one over the other in the process (paper movement) direction, so that the arrays extend normal to the direction of scanning. In the side-by-side full color printing arrangement, the information on a single line is recorded by selectively operating all of the heads, as needed, in each line pass. In the stacked full-color arrangement a single color head is selectively fired during each line pass, so that at least three passes are necessary to complete the information needed for each line. When it is desred to accomplish monochrome printing with the full-color and highlight color devices, a single recording head (usually black) is fired for each line pass. All other cartridges will be inoperative.
During the design phase of the development of an ink jet scanning printer, the maximum speed of recording is achieved by optimizing the several operational parameters which control the maximum speed of the scanning carriage. These are, among others, the number of nozzles in the marking head array, the drop generation rate, the drop velocity, the carriage motor characteristics, and the data rate. While it is sometimes possible to increase the speed of recording by a small increment, such a change is often inconvenient or trivial in a given printer.
It is an object of the present invention to multiply the printing speed of a multi-color printer, when operated in the monochrome mode, by a factor of two or three, or more by selectively vertically repositioning at least one of the cartridge holders so that at least two cartridges of the same color will be able to print simultaneously at least two adjacent lines during a single line scan.
It is a further object of the present invention to provide a dynamic elevating arrangement which will simply, efficiently and accurately move the repositionable holder and its cartridge to a raised position.
It is another object of the present invention to provide a static elevating arrangement in which the cartridge holder is designed to accept a repositionable cartridge only in an elevated position.
It is another object of the present inventin to provide a monochrome printer with the capability of printing a second line simultaneously at different selected line spacings.